# year    value 
 1901 12.34063 
 1902 12.28869 
 1903  12.2041 
 1904 12.19716 
 1905 12.68391 
 1906 12.32121 
 1907 12.16666 
 1908 12.11805 
 1909 12.68024 
 1910  11.9195 
 1911  12.0005 
 1912 11.84511 
 1913 12.30507 
 1914 12.28163 
 1915 12.93858 
 1916 11.97536 
 1917 12.02424 
 1918 12.20703 
 1919 12.12708 
 1920 12.57818 
 1921 12.08332 
 1922 12.41797 
 1923 12.27822 
 1924 12.28755 
 1925 12.74181 
 1926  12.1699 
 1927 12.69534 
 1928 12.29617 
 1929 12.25412 
 1930 12.26357 
 1931 12.40343 
 1932 12.45997 
 1933 12.37422 
 1934 11.74352 
 1935  12.4786 
 1936 12.93966 
 1937 12.21858 
 1938 12.46696 
 1939 12.53307 
 1940 12.85662 
 1941   12.928 
 1942 12.98942 
 1943 12.45749 
 1944 12.27393 
 1945 12.99667 
 1946 12.86697 
 1947 12.59119 
 1948  12.2158 
 1949 12.03288 
 1950 11.64496 
 1951 12.88766 
 1952 12.03274 
 1953 12.31774 
 1954 12.35784 
 1955 12.42783 
 1956 12.13627 
 1957 12.24707 
 1958  12.2709 
 1959 12.40879 
 1960 12.21684 
 1961 12.29166 
 1962 11.92394 
 1963 12.77315 
 1964 12.30844 
 1965 12.72074 
 1966 12.08745 
 1967 11.79184 
 1968  12.3078 
 1969 12.42396 
 1970 12.20956 
 1971 12.45497 
 1972 12.29647 
 1973 12.44934 
 1974 12.50597 
 1975 12.51517 
 1976 11.96941 
 1977 13.02242 
 1978 12.69779 
 1979 12.62982 
 1980 13.15333 
 1981 11.95926 
 1982 12.62642 
 1983 12.97288 
 1984 12.33954 
 1985 12.21318 
 1986 12.27705 
 1987 12.65885 
 1988 13.06613 
 1989 12.83243 
 1990 13.27877 
 1991 12.61768 
 1992  12.1089 
 1993 12.28485 
 1994 12.80356 
 1995 13.12282 
 1996 12.53474 
 1997 12.34413 
 1998 13.75409 
 1999 13.36826 
 2000 12.47977 
 2001 13.41676 
 2002 12.99567 
 2003 13.10484 
 2004 13.03046 
 2005 13.52595 
 2006  13.8585 
 2007 13.20809 
 2008 13.41463 
 2009 13.11564 
 2010 13.56018 
 2011 13.31396 
 2012  12.6324 
 2013 13.29827 
 2014 13.33878 
 2015 13.34485 
 2016  13.1777 
 2017 13.54477 
 2018 12.81052